1. Technical Field
Embodiments of the present invention relate to a composition for filling small gaps in a semiconductor device (also referred to simply as a ‘gap-filling composition’), and more particularly to a node separation polymer (NSP) composition with excellent shelf life that is suitable for use in the fabrication of a semiconductor capacitor.
2. Background Art
Schematic diagrams illustrating a node separation process for the fabrication of a conventional semiconductor capacitor are shown in FIG. 1. First, Ti/TiN as an electrode material is applied to an oxide mold (i.e., an oxide for patterning), and then patterned holes are filled with a node separation polymer (NSP) composition (i.e., a gap-filling composition). Thereafter, the resulting structure is developed with a developing solution to remove the NSP material coated on the top portions of the electrode material layer, followed by baking. Etch back is performed to remove the top portions of the electrode material layer. Next, wet etching and ashing are sequentially performed to remove the oxide and the NSP material, respectively. If the said NSP materials are applied to patterned holes having smaller hole size, the surface of TiN is toughened during ashing, which causes difficulty in applying dielectric materials in the subsequent step. As semiconductor devices become smaller in size and thickness, there is a strong need for novel node separation polymer (NSP) materials that can eliminate the need for ashing. The use of such NSP materials can be expected to contribute to the simplification of processing equipment and the reduction of fabrication costs. FIG. 2 illustrates a node separation process for the fabrication of a semiconductor capacitor without the need for ashing.
A novel NSP material capable of eliminating the need for ashing is filled in patterned holes and is then removed by wet etching using a hydrofluoric acid solution for the removal of an oxide for patterning. It is anticipated that a silicone polymer having a basic structure similar to that of the oxide or a composition comprising the silicone polymer would be effective as the NSP material.
However, a general silicone polymer undergoes slow self-condensation between terminal hydroxyl (—OH) groups. This self-condensation deteriorates the shelf life of a composition comprising the polymer. Particularly, the dissolution rate (DR) of the NSP material must be maintained constant during development, which is the most important step in NSP processing, in every process. Therefore, self-condensation results in a gradual increase in the molecular weight of the polymer to retard the dissolution rate of the NSP material.